VIENNA — The U.N. nuclear agency has told member nations that Iran is poised for a major technological upgrade of its uranium enrichment program, in a document seen today by The Associated Press. The move would vastly speed up Tehran’s ability to make material that can be used for both reactor fuel and nuclear warheads.

In an internal note to member nations, the International Atomic Energy Agency said it received notice last week from Iran’s nuclear agency of plans to install high-technology enriching centrifuges at its main enriching site at Natanz, in central Iran. The machines are estimated to be able to enrich up to five times faster than the present equipment.

A senior diplomat familiar with the issue said it would take weeks or months to have the new machines running once technicians started putting them in.

The planned upgrade deals a further blow to international efforts to coax Tehran to restore confidence in its aims by scaling back its nuclear activities and cooperating with agency attempts to investigate allegations of secret weapons work.